1. Field of the Invention
The present invention relates to battery charging control units and methods for controlling battery charging. More specifically, the present invention relates to a battery charging control unit for batteries used, for instance, for an electric vehicle, and a method for controlling the charging of such batteries.
2. Description of Related Art
In general, processes of charging, discharging, and recharging batteries are repeated when batteries are used. If the batteries are used for a certain period of time and these processes of charging and discharging are repeated a considerable number of times, the level of a full charge, i.e., the level at which the batteries are a fully charged to their maximum charging capacity, as compared with the initial level of full charge of the batteries, will decrease.
If this decrease in the charging capacity is caused temporarily by such factors as memory effect, it is known that the batteries can be restored to some extent by carrying out a supplemental charging (i.e., a complete charging/discharging) of the batteries.
As disclosed in the Japanese Unexamined Patent Application, First Publication No. 62-260531, for instance, the decrease in the charging capacity of the batteries can be restored by carrying out a supplemental charging process (or an even charging process) each predetermined number of times that the battery is charged.
However, among the environments in which the battery is used, there are cases in which, depending on the condition of the battery, supplemental charging of the batteries should not be carried out. In particular, when the battery is installed in an electric automobile, for example, the environments in which it is used may vary drastically. The batteries may be used in a harsh temperature environment wherein the temperature of the batteries reaches more than 40xc2x0 C. during summer and less than xe2x88x9210xc2x0 C. during winter.
Also, when batteries are in a high temperature environment, there is a danger that the batteries may be damaged by the supplemental charging process because in such an environment the charging current may be consumed in generating heat that increases the temperature of the batteries rather than being used to charge the batteries. Moreover, since a certain amount of the charging current is consumed for generating heat, the electric power is wasted and is economically ineffective.
In consideration of the above, an object of the present invention is to provide a battery charging control unit which is capable of eliminating the problem of the insufficient charging capacity of batteries by carrying out a supplemental charging process reliably at a suitable timing so that a highly efficient state of the batteries may be maintained and the lifetime thereof may be extended.
The present invention provides a battery charging control unit which controls the electric power from a power source and supplies it to a battery via a charger, comprising: a charging capacity insufficiency detection unit which detects an insufficiency in charging capacity of the battery based on the previous charging condition of the battery, the charging capacity insufficiency detection unit being capable of storing the detected insufficiency in the charging capacity of the battery; a charging capacity restoring determination unit which, after the charging capacity insufficiency detection unit detects an insufficiency in charging capacity of the battery, determines if the insufficiency in charging capacity of the battery will be restored by carrying out a supplemental charging process for the battery; and a supplemental charging unit which carries out the supplemental charging process for the battery if the charging capacity insufficiency detection unit detects an insufficiency in the charging capacity of the battery and the charging capacity restoring determination unit determines the insufficiency in charging capacity of the battery will be restored by the supplemental charging process.
As shown in FIG. 8, the restoring of a battery having a charging capacity insufficiency carried out by a supplemental charging process is confirmed to be effective if such a charging operation is performed after the temperature of the battery has been lowered, for instance, to an ordinary temperature. In consideration of this fact, the above battery charging control unit according to an embodiment of the invention has a structure capable of reliably restoring a battery having a charging capacity insufficiency by performing a suitable supplemental charging operation.
Specifically, the charging capacity insufficiency detection unit of the above battery charging control unit stores the charging condition (or state) of the battery in the previous charging operations in memory and carries out a supplemental charging operation based on the data of the previous charging condition stored in the memory. Also, the charging capacity restoring determination unit determines if the insufficiency in charging capacity of the battery will be restored by carrying out a supplemental charging process for the battery. This is because the restoring of the battery having a charging capacity insufficiency is difficult even with the supplemental charging operation if the temperature is high, as mentioned above, and the charging capacity restoring determination unit determines to carry out a supplemental charging process by the supplemental charging unit only when the restoring of the battery by the supplemental charging operation may be expected based on the battery temperature or the outside air temperature.
That is, the supplemental charging process is carried out only when the charging capacity insufficiency is detected and the restoring of battery is expected. Accordingly, it becomes possible to avoid performing a supplemental charging process when unnecessary. Also, harmful effects to the batteries, such as a temperature increase thereof due to the supplemental charging process or the waste of charging time and energy, may be avoided.
Moreover, since the charging capacity insufficiency detection unit only detects and stores in memory the generation of charging capacity insufficiency and does not carry out a supplemental charging process if the charging capacity restoring determination unit determines that the restoring of the battery is not expected, i.e., the supplemental charging process is carried out only when the restoring of battery is expected, and thus it becomes possible to carry out the supplemental charging process reliably.
Further, problems associated with a conventional periodic supplemental charging process, in which the process may be carried out unnecessarily, may be eliminated, simply resulting in an increase in the temperature of batteries that may shorten their life.
In accordance with another aspect of the invention, the charging capacity restoring determination unit determines if the battery will be restored by the supplemental charging process based on at least one of the battery temperature, and the outside air temperature.
According to the above battery charging control unit, since the charging capacity restoring determination unit determines if the battery will be restored by the supplemental charging process based on at least one of a battery temperature, and an outside air temperature, reliably carrying out the supplemental charging process to restore the battery when the restoring thereof is expected becomes possible.
Also, causing harmful effects to the battery, which may occur if a supplemental charging process is carried out when the temperature of battery or outside air is extremely high, may be avoided. Moreover, saving the time and energy that would be wasted if an unnecessary supplemental charging operation is performed becomes possible.
In yet another aspect of the invention, a battery charging control unit further includes: an integrated calendar, wherein the charging capacity restoring determination unit determines if the battery will be restored by the supplemental charging process based on the integrated calendar.
According to the above battery charging control unit, data for dates, months, or seasons, or information relating to annual temperature change may be input into the integrated calendar so that the charging capacity restoring determination unit may determine if the battery will be restored by a supplemental charging process based on the data contained in the integrated calendar. Therefore, it becomes possible, for instance, to effectively restore the battery by carrying out supplemental charging processes mainly in spring or fall, when the restoring of the battery is highly expected, and avoid a season such as summer or winter, when there is little expectation of the restoring of the battery.
In yet another aspect of the invention, a battery charging control unit further includes a point counter, wherein the charging capacity insufficiency detection unit is capable of calculating a degree of the insufficiency in charging capacity of the battery by adding a certain predetermined point, which is based on the previous charging condition of the battery, to the point counter, and the supplemental charging unit is capable of carrying out the supplemental charging process when points in the point counter exceed a predetermined value.
According to the above battery charging control unit, the previous charging condition or state of the battery may be converted into numerical points and the points may be accumulated in the point counter so that a supplemental charging process by the supplemental charging unit may be reliably carried out for the battery based on the information obtained from the accumulated points.
In yet another aspect of the invention, the charging capacity insufficiency detection unit adds a certain number of points to the point counter if a charging process for charging the battery is terminated before being finished.
According to the above battery charging control unit, the effect of terminating a charging process before being finished may be converted into a point and this point is accumulated so that such an effect may be reflected in subsequent charging processes to carry out the processes reliably.
In yet another aspect of the invention, the charging capacity insufficiency detection unit adds a certain number of points to the point counter if a charging process for charging the battery is temporarily stopped due to a temperature rise in the battery exceeding a first predetermined temperature.
According to the above battery charging control unit, the effect of temporarily stopping a charging process due to a temperature rise in the battery exceeding a first predetermined temperature may be converted into a point and the point is accumulated so that such an effect may be reflected in subsequent charging processes. That is, since the increase in battery temperature during a charging process can be a factor for causing a charging capacity insufficiency, the factor is converted into a point and the point is accumulated so that a subsequent charging process may be carried out reliably.
In yet another aspect of the invention, the charging capacity insufficiency detection unit adds a certain number of points to the point counter if the temperature of the battery is greater than a second predetermined temperature upon the completion of the charging process.
According to the above battery charging control unit, the effect of the temperature of the battery greater than a second predetermined temperature upon the completion of the charging process may be converted into a point and the point is accumulated so that such an effect may be reflected in subsequent charging processes. That is, since an extremely high temperature of the battery at the completion of the charging process can be a factor for causing a charging capacity insufficiency, the factor is converted into a point and the point is accumulated so that a subsequent charging process may be carried out reliably.
In yet another aspect of the invention, the supplemental charging unit determines a charging manner in the supplemental charging process based on the level of charging capacity insufficiency detected by the charging capacity insufficiency detection unit.
According to the above battery charging control unit, the supplemental charging unit may reliably restore the battery by carrying out a supplemental charging process using a most suitable charging manner (i.e., charging current, charging time, ampere-hour, etc.) for the battery based on the level of charging capacity insufficiency detected by the charging capacity insufficiency detection unit. That is, if the level of the charging capacity insufficiency is large, the supplemental charging magnitude is increased to achieve an early restoring of the battery and, if the level of the charging capacity insufficiency is small, the supplemental charging magnitude is decreased to achieve a restoring of the battery in an unforced manner.
In yet another aspect of the invention, the charging capacity insufficiency detection unit subtracts, after the completion of the supplemental charging process by the supplemental charging unit, a certain number of points from the point value accumulated in the point counter.
According to the above battery charging control unit, since a certain number of points, which corresponds to the level of battery restoring by the supplemental charging process, are subtracted from the point value in the point counter by the charging capacity insufficiency detection unit, the level of battery restoring by the supplemental charging process may be reflected as points so that the state or condition of the battery may be reliably accumulated in the point counter as a numerical point value.
In yet another aspect of the invention, the points subtracted from the point value in the point counter is predetermined in accordance with the temperature of the battery at the completion of the supplemental charging process.
According to the above battery charging control unit, since the subtracted points which correspond to the degree of restoration of the battery by a supplemental charging process are predetermined based on the battery temperature, the points subtracted may be increased in the temperature range in which a significant restoring of the battery is expected and the points subtracted may be decreased in the temperature range in which there is little expectation that the battery will be restored. Accordingly, the difference in the level of battery restoring due to the difference of the battery temperature may be accurately reflected as subtracted points, and the points may be subtracted from the point value in the point counter so that the state or condition of the battery may be reliably accumulated in the point counter as a point value.
In yet another aspect of the invention, the points subtracted from the point value in the point counter is predetermined in accordance with the charging magnitude of the supplemental charging process.
According to the above battery charging control unit, since the subtracted points, which correspond to the degree of restoration of the battery by a supplemental charging process, are predetermined based on the charging current of the supplemental charging process, the level of restoring of the battery corresponding to the charging magnitude of supplemental charging process may be accurately reflected as a subtracted points by increasing the subtracted points when the charging magnitude is large and decreasing the subtracted points when the charging magnitude is small, and the point may be subtracted from the point value in the point counter so that the state or condition of the battery may be reliably accumulated in the point counter as a point value.
In yet another aspect of the invention, the points subtracted from the point value in the point counter are predetermined in accordance with the number of the supplemental charging processes performed by the supplemental charging unit.
According to the above battery charging control unit, since the subtracted points, which correspond to the degree of restoration of the battery by a supplemental charging process, are predetermined based on the number of supplemental charging processes, the level of the restoring of the battery, which decreases as the number of supplemental charging processes increases, may be accurately reflected as subtracted points, and the points may be subtracted from the point value in the point counter so that the state or condition of the battery may be reliably accumulated in the point counter as a point value.
The present invention also provides a method for controlling battery charging by controlling a power from a power source and supplying it to a battery via a charger, including the steps of: (a) carrying out a charging capacity insufficiency detection process to determine whether the charging capacity of the battery is insufficient or not; (b) carrying out a restoring effect determination process that determines if the charging capacity insufficiency in the battery will be restored by a supplemental charging process; and (c) carrying out a supplemental charging process of the battery to restore the charging capacity insufficiency of the battery if it is determined that the charging capacity of the battery is insufficient in the charging capacity insufficiency detection process and that the battery will be restored by the supplemental charging process in the restoring effect determination process.
In accordance with another aspect of the present invention, whether the battery will be restored by the supplemental charging process is determined in the restoring effect determination process based on information of at least one of a battery temperature and an outside air temperature.
In yet another aspect of the invention, the charging capacity insufficiency detection process includes the steps of: (i) determining if the charging process is terminated prior to the completion of the charging process, and adding a certain number of points if it is determined that the charging process has been terminated before completion; (ii) determining if the charging process has been temporarily stopped because of a temperature rise in the battery that is higher than a first predetermined temperature, and adding a certain number of points if it is determined that the charging process is temporarily stopped because of a temperature rise in the battery that is higher than the first predetermined temperature; and (iii) determining if the temperature of the battery is higher than a second predetermined temperature when the charging process is completed, and adding a certain number of points if it is determined that the battery temperature is higher than the second predetermined temperature when the charging process is completed.
In yet another aspect of the invention, the charging capacity insufficiency detection process further including the steps of: (iv) accumulating the points obtained in the steps (i) through (iii) and determining if the accumulated points are greater than a first predetermined number of points; and (v) correcting the accumulated point, if the accumulated point is greater than the first predetermined point, so that the accumulated points is set equal to the first predetermined point.
In yet another aspect of the invention, the supplemental charging process including the steps of: (i) determining if the accumulated point is greater than a second predetermined point when the supplemental charging process is started; (ii) carrying out a supplemental charging process of the battery in a relatively heavy manner if it is determined that the accumulated point is equal to or greater than the second predetermined point in step (i); and (iii) carrying out a supplemental charging process of the battery in a relatively light manner if it is determined that the accumulated point is smaller than the second predetermined point in step (i).
In yet another aspect of the invention, a method for controlling battery charging further includes the step of: (d) carrying out a point value correction process which includes the steps of: (i) determining whether the battery temperature is equal to or higher than a third predetermined temperature, and subtracting a certain number of points if it is determined that the battery temperature is equal to or higher than the third predetermined temperature; (ii) determining whether the battery temperature is lower than a fourth predetermined temperature, and subtracting a certain number of points if it is determined that the battery temperature is lower than the fourth predetermined temperature; and (iii) determining whether the battery temperature is in the range between the third and the fourth predetermined temperatures, and subtracting a certain number of points which corresponds to the current magnitude and the number of charging processes performed if it is determined that the battery temperature is in the range between the third and the fourth predetermined temperatures.
In yet another aspect of the invention, the point value correction process further including the steps of: (iv) calculating the total of the points obtained in the steps (i) through (iii) of the charging capacity insufficiency detection process and the points subtracted in the steps of (i) through (iii) of the point value correction process, and determining if the accumulated point is greater than a third predetermined point; and (v) correcting the calculated total point, if the total point is less than zero, so that the calculated point be zero.
In yet another aspect of the invention, whether the charging capacity of the battery is insufficient or not in the charging capacity insufficiency detection process is determined based on the calculated total points.
As mentioned above, it is confirmed that the restoring of a battery having a charging capacity insufficiency carried out by a supplemental charging process is effective if such a charging operation is performed after the temperature of the battery is lowered, for instance, to the ordinary temperature. In consideration of this fact, the above method for controlling battery charging according to an embodiment of the invention is capable of reliably restoring a battery having a charging capacity insufficiency by performing a suitable supplemental charging operation.
That is, the charging capacity insufficiency detection process and the supplemental charging process in the above method for controlling battery charging of the present invention may be carried out based on data of the previous charging condition stored in memory. Also, in the charging capacity restoring effect determination process, it is determined if the insufficiency in charging capacity of the battery will be restored by carrying out a supplemental charging process for the battery. This is because the restoring of the battery having a charging capacity insufficiency is difficult even by carrying out the supplemental charging process if the temperature of battery or that of outside air is high. Accordingly, a supplemental charging process is performed only when the charging capacity insufficiency is detected and the restoring of battery is expected. Therefore, performing a supplemental charging process when unnecessary can be avoided. Also, harmful effects on the batteries, such as a temperature increase thereof due to the supplemental charging process or the waste of charging time and energy, may be avoided.
Moreover, since a supplemental charging process is not carried out if it is determined that the restoring of the battery is not expected by the restoring effect determination process, i.e., the supplemental charging process is carried out only when the restoring of battery is expected, the supplemental charging process can be reliably carried out.
Further, problems associated with a conventional periodic supplemental charging process, wherein the process may be carried out when it is unnecessary and simply result in an increase in the temperature of batteries which may shorten their life, may be eliminated.
In addition, since if the battery will be restored by the supplemental charging process is determined in the restoring effect determination process based on information of at least one of the battery temperature, the outside air temperature, and the integrated calendar, the supplemental charging process to restore the battery when the restoring thereof is expected can be reliably carried out.
Also, the harmful effects on the battery that may be caused if a supplemental charging process is carried out when the temperature of battery or outside air is extremely high become avoidable. Moreover, the time and energy that would be wasted if an unnecessary supplemental charging operation is performed can be saved.